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Why Did the Steps of CPR change from A-B-C to C-A-B?

Does the thought of putting your mouth on the mouth of a total stranger give you the heebie-jeebies? Even if you’re aware of CPR’s role in saving lives, you may think twice about performing mouth-to-mouth resuscitation because of the fear of getting an infection.

The good news is that in 2010, the American Heart Association (AHA) changed CPR’s longstanding A-B-C (Airway, Breathing, Compressions) sequence to C-A-B (Compressions, Airway, Breathing). The old A-B-C sequence for CPR consisted of the following steps:

  1. Airways – Tilt the victim’s head and lift his chin to open the airway
  2. Breathing – Pinch the victim’s nose and breathe into the mouth
  3. Compressions – Apply pressure to the victim’s chest

The new C-A-B (Compressions, Airway, Breathing) sequence teaches rescuers to perform chest presses before anything else. But after four decades, why did the AHA implement such a drastic change? There is a lot of buzz surrounding the A-B-C to C-A-B update because it requires anyone who learned CPR previously to get re-educated, but the AHA thinks the pros outweigh the cons.

The Science behind the Decision

In an adult who has been breathing normally, there is enough oxygen in the blood to supply the heart and the brain for several minutes following cardiac arrest. Chest compressions are needed, however, to circulate the oxygen and ensure that it is distributed quickly.

Rescue breaths are thought to be harmful because they require the rescuer to stop doing chest compressions for several seconds. Additionally, rescue breaths lower air pressure in the chest cavity, which in turn slows down circulation, a key factor in resuscitation. If the rescuer does chest compressions first, the victim gains approximately 30 seconds of time in his favor.

When people follow the A-B-C sequence to perform CPR, there is often a significant delay because they spend so much time trying to open the airway, make an air-tight seal around the mouth, or get over their reluctance to do mouth-to-mouth resuscitation. With the new C-A-B sequence, people initiate chest compressions sooner and ventilation is only slightly delayed. The AHA also predicts that the number of people who receive CPR will increase because of this change, since bystanders often balk at the idea of performing mouth-to-mouth resuscitation on a total stranger.

However, the change from A-B-C to C-A-B only applies to adult victims of sudden cardiac arrest. For children and in cases of asphyxia arrest, drug overdose, or near-drowning among adults, rescuers are still recommended to follow the A-B-C sequence.


What Else Is New?

AHA’s new guidelines also call for faster and more forceful compressions. They recommend that rescuers compress the chest by at least two inches on each push and perform a minimum rate of 100 compressions per minute.

In addition, the new guidelines strongly advise 911 dispatchers to guide callers in “compression-only” CPR. Their recommendation that untrained bystanders perform compression-only CPR still stands.